IP with 11mm and shimmed gov..problems

[55eta]

@anto   the whole principle of the dynamic timing advance on ve pums is based on pressure i.e as rpm increase pressure increases which then acts on the advance piston which then in turn moves the timing ring [ more rpm=more pressure= more movement] , if the pressure is increased at tick over it will prematurely increases throughout the rev range and you would reach max advance prematurely and run advanced timing from tick over ,The IPR and overflow valve are finely balance to create  a internal pressure at a given p.s.i  which the advance piston  and spring rate is calibrated to ,so if you increase the pressure without increasing the spring rate  your dynamic timing will be advanced when your static timing is spot on so if  your engine sounds a bit clacky since you increased IP it could be worth increasing the spring rate by adding a shim or 2 ,or swap the IPR, over flow valve and spring from transit and have it all balanced but weather the balanced option would give a performance gain i would not like to say,but it would cure any timing advance problems       as for cavitation it is basically the creation of shock waves that are capable of dissolving metal in the same way as ultra sonic cleaning works.   P.S would be interested in the results if you shim the spring as i am building a 11mm pump but was going for the balanced option as it worked with a 10mm head  so i was planing to use IPR ,O/F valve + ADV spring from transit with the same mod on the advance as you .As for DARENJLOB im just wondering weather the positive increase in performance that he gained by increasing IPR rate could have been from over shimming when when modding advance spring which can cause dynamic timing to be retarded which would give you a lack of power at higher rpm ,and when he increased the internal pressure he advanced dynamic timing [JUST A THOUGHT ] as i can not see how you can gain  a significant  increase of power by increasing IP rates as the increase in pressure on the high pressure side of the pump would be a very small increase in pressure, other than in big big horsepower engines where they are suffering from a lack of fuel flow  [but i could be wrong on that]

[anto]

Cheers 55eta you have given me a few things to think about for tonight....
Il report back with my findings.
At the minute i am using the transit IPR, but i am using the 306 springs and shims in the advance cover.
So basically i am hitting full advance way to early, which would explain alot. I am basically hitting full advance, say, at 3500rpm as opposed to 5000rpm, this is also causing me too much advance at idle meaning i had to retard static advance to stop the clatter at idle.

[55eta]

@anto it could be worth swapping the over flow valve on your pump for the transit one then setting static timing and see if you get better topend power  if that do prove to be the case it is then worth shimming the advance spring to increase the rate then replace the overflow valve which would then increase the internal pressure in the pump an hopefully sort out your problem PS most IDI engines reach max advance at 3800to 4600 with stock bosch advance systems ,unless you lengthen the slot in the pump body and shorten the piston and /or shim out the end caps i would be verey intrested in the results as  the pump im building is for aT4 and to gain any acese to the pump means complet removal of the front end +cooliing system

[anto]

55eta - when you say overflow valve do you mean the fuel outlet that heads back to the tank?
I am already using the transit IPR.
So use both the transit IPR and outlet/ overflow valve set static timing and see what its like?

Im tempted to go back to my 9mm pump for a while and see what differences there are.

[55eta]

yes that is the valve it has small holes on the inside ,if the holes on the stock one are smaller or less of them it will increase internal pressure by quite abit .iam not 100% sure but think the IPR on the transit is a higer rate to increase flow not pressure so the over flow valve from the transit should have larger holes or more of them to keep the pressure down but maintian the inreased flow b ut like i said not 100% sure but still worth lookign at as it is not that time consuming as swaping pumps and shimming advance spring ,or you could just replace stock IPR and set static timing ,if it is still the same i would be looking at the advance mod you done .when i built my 10mm pump i did each mod one at atime so if i had change in perfomance weather it was+or- i knew what the cause was as it is far easyer to solve 1 problerm at atime

[anto]

Unfortunately i was unable to use the overflow valve from the transit as it physically wouldnt fit in the 306 lda hole (too long).
So im still using the transit IPR and 306 overflow valve for the meantime...

[darrenjlobb]

SO does anyone know if all VE levers (black levers that connect to control collar) are the same in terms of travel?

Basically i have a selection of camplates here now.. and i have some that have 1mm extra plunger travel, but im thinking, unless the collor moves enuf anyway to acommadate it, it wont matter how big the camplate it, is the plunge is always gunna pass the collar at the same point and stop injecting....or does the collar move easily far enuf along anyway?

[anto]

Darren i havent had a chance to compare the levers again il hopefully get time this week smetime...